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Strong ground motion of the San Fernando, California, earthquake: Ground displacements

Hanks, Thomas C. (1975) Strong ground motion of the San Fernando, California, earthquake: Ground displacements. Bulletin of the Seismological Society of America, 65 (1). pp. 193-225. ISSN 0037-1106.

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Two hundred and thirty-four components of ground displacement are the basis of an investigation of long-period strong ground motion in southern California arising from the San Fernando, California, earthquake. The displacement data are obtained from the double integration of strong-motion accelerograms via the base-line adjustment and filtering operations routinely performed in the series “Strong Motion Earthquake Accelerograms”. These procedures can recover long-period data from strong-motion accelerograms with considerable accuracy. Many-station comparisons of displacement data for which the station spacing is small compared to the wavelengths of interest reveal that uncertainties in displacement are less than 1 cm in the period range 5 to 8 sec, 1 to 2 cm at periods near 10 sec, and 2 to 4 cm in the period range 10 to 15 sec, for a data sensitivity of approximately 7.6 cm/g. For limited variations in epicentral distance (R) and source-station azimuth (ϕ), ground displacements show a strong coherence; for wider variations in R and ϕ, many of the observed variations in the displacement wave forms are easily attributable to well-understood seismological phenomena. Seismic moment, source dimension, radiation pattern, rupture propagation, the development of surface waves and their subsequent dispersion, and azimuthal variations in the gross geological structure all appear to have first-order significance in fashioning the gross amplitude and frequency content of the displacement wave forms and in explaining observed variations with R and ϕ. The essential simplicity of these displacement wave forms offers considerable optimism that long-period strong ground motion can be realistically synthesized with advance knowledge of the earthquake source parameters and gross geological structure.

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Additional Information:Copyright © 1975, by the Seismological Society of America. Manuscript received May 9, 1974. I appreciate the efforts of Joseph Galvan, Vincent Lee, Laszlo Lenches, James Justiss, Barbara Turner, and Sharon Vedrode in various stages of data manipulation and manuscript preparation. D. E. Hudson, G. W. Housner, and M. D. Trifunac have offered valuable comments during several phases of this investigation. C. R. Allen, H. Kanarnori, R. B. Matthiesen, and O. W. Nuttli critically read the manuscript. This research was supported in part by the National Science Foundation, the Earthquake Research Affiliates Program of the California Institute of Technology, and the Advanced Research Projects Agency of the Department of Defense, as monitored by Air Force Office of Scientific Research under contract F44620-72-C-0078.
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Caltech Earthquake Research AffiliatesUNSPECIFIED
Advanced Research Projects Agency (ARPA)UNSPECIFIED
Air Force Office of Scientific Research (AFOSR)F44620-72-C-0078
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Caltech Division of Geological and Planetary Sciences2473
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ID Code:48406
Deposited By: George Porter
Deposited On:12 Aug 2014 21:06
Last Modified:13 Feb 2019 18:06

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